Safety improvements for UV radiation in aquatic applications

ABSTRACT

The invention provides an object ( 10 ) that during use is at least partly submerged in water, the object ( 10 ) further comprising an anti-bio fouling system ( 200 ) comprising an UV emitting element ( 210 ), wherein the UV emitting element ( 210 ) comprises one or more light sources ( 220 ) and is configured to irradiate with UV radiation ( 221 ) during an irradiation stage one or more of (i) a part ( 111 ) of an external surface ( 11 ) of said object ( 10 ) and ( ii ) water adjacent to said part ( 111 ) of said external surface ( 11 ), wherein the object ( 10 ) is selected from the group consisting of a vessel ( 1 ) and an infrastructural object ( 15 ), wherein the object ( 10 ) further comprises a water switch ( 400 ), wherein the anti-bio fouling system ( 200 ) is configured to provide said UV radiation ( 221 ) to said part ( 111 ) in dependence of the water switch ( 400 ) being in physical contact with the water.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2016/061895, filed on 26May 2016, which claims the benefit of European Patent Application No.15170616.5, filed on 3 Jun. 2015. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to an object that during use is at least partlysubmerged in water, especially a vessel or an infrastructural object.

BACKGROUND OF THE INVENTION

Anti-biofouling methods are known in the art. US2013/0048877, forinstance, describes a system for anti-biofouling a protected surface,comprising an ultraviolet light source configured to generateultraviolet light, and an optical medium disposed proximate to theprotected surface and coupled to receive the ultraviolet light, whereinthe optical medium has a thickness direction perpendicular to theprotected surface, wherein two orthogonal directions of the opticalmedium orthogonal to the thickness direction are parallel to theprotected surface, wherein the optical medium is configured to provide apropagation path of the ultraviolet light such that the ultravioletlight travels within the optical medium in at least one of the twoorthogonal directions orthogonal to the thickness direction, and suchthat, at points along a surface of the optical medium, respectiveportions of the ultraviolet light escape the optical medium.

U.S. Pat. No. 5,308,505 describes that biofouling of underwater surfacesby marine organisms is prevented by irradiating the water withultraviolet light and adjusting the intensity of the ultraviolet lightso as to kill barnacle larvae to prevent their attachment to theunderwater surface. Further, this document describes that the water ispassed through a biocidal chamber having a source of ultraviolet lightat an intensity of at least 4000 mu watts/cm² and at a rate to provide aresidence time of at least one minute on the biocidal chamber. Thisdocument further describes that as the turbidity of the sea waterbetween the assembly and the grating changes, an ultraviolet sensor, forexample an ultraviolet sensitive diode, detects the intensity changes,and provides corresponding signals through the cable to a sensor controlunit. The ultraviolet light intensity fluctuations are processed toprovide a feedback signal to the lamp intensity unit. The intensity fromthe ultraviolet lamps at the grating is automatically adjusted in thisway to maintain a minimum 20 μwatt/cm² distribution over the irradiatedarea. Further, this document describes a flexible opaque cover extendedout to the boat from the pier to keep the ultraviolet light which can beharmful to the human eye from escaping. An array of ultravioletlight/reflector assemblies are moved into position by a positioningmechanism attached to a pier near the boat's hull. Contact sensors onthe array determine the proper position of the array for application ofthe correct ultraviolet intensity to the hull.

SUMMARY OF THE INVENTION

Biofouling or biological fouling (herein also indicated as “fouling”) isthe accumulation of microorganisms, plants, algae, and/or animals onsurfaces. The variety among biofouling organisms is highly diverse andextends far beyond attachment of barnacles and seaweeds. According tosome estimates, over 1700 species comprising over 4000 organisms areresponsible for biofouling. Biofouling is divided into microfoulingwhich includes biofilm formation and bacterial adhesion, andmacrofouling which is the attachment of larger organisms. Due to thedistinct chemistry and biology that determine what prevents organismsfrom settling, these organisms are also classified as hard or softfouling types. Calcareous (hard) fouling organisms include barnacles,encrusting bryozoans, mollusks, polychaete and other tube worms, andzebra mussels. Examples of non-calcareous (soft) fouling organisms areseaweed, hydroids, algae and biofilm “slime”. Together, these organismsform a fouling community.

In several circumstances biofouling creates substantial problems.Machinery stops working, water inlets get clogged, and hulls of shipssuffer from increased drag. Hence the topic of anti-fouling, i.e. theprocess of removing or preventing fouling from forming, is well known.In industrial processes, bio-dispersants can be used to controlbiofouling. In less controlled environments, organisms are killed orrepelled with coatings using biocides, thermal treatments or pulses ofenergy. Non-toxic mechanical strategies that prevent organisms fromattaching include choosing a material or coating with a slipperysurface, or creation of nanoscale surface topologies similar to the skinof sharks and dolphins which only offer poor anchor points. Biofoulingon the hull of ships causes a severe increase in drag, and thusincreased fuel consumption. It is estimated that an increase of up to40% in fuel consumption can be attributed to biofouling. As large oiltankers or container transport ships can consume up to €200.000 a day infuel, substantial savings are possible with an effective method ofanti-biofouling.

It surprisingly appears that one may effectively use UV radiation tosubstantially prevent biofouling on surfaces that are in contact withsea water or water in lakes, rivers, canals, etc. Herewith, an approachis presented based on optical methods, in particular using ultra-violetlight or radiation (UV). It appears that most micro-organisms arekilled, rendered inactive or unable to reproduce with sufficient UVlight. This effect is mainly governed by the total dose of UV light. Atypical dose to kill 90% of a certain micro-organism is 10 mW/h/m².However, in most of these embodiments, there may be some UV radiationthat may reach places it is not intended to go. This basically coverseverything above the waterline, and especially human beings in closeproximity to the aquatic application. During cruise at open sea, thismay not happen (even though it is to be mentioned that personnel onboard of the vessel might still face a (tiny) risk), but while e.g.being docked in a harbor the risk is larger, as more people move nearthe boat. This can include dock workers, crane operators, supply vesselsmooring near the ship (on the non-dock side), etc.

Hence, it is an aspect of the invention to provide an alternative systemor method for prevention or reduction of biofouling, which preferablyfurther at least partly obviates one or more of above-describeddrawbacks.

In a first aspect, the invention provides an object that during use isat least partly submerged in water, the object further comprising ananti-biofouling system (which may also be indicated as “anti-foulinglighting system”) comprising an UV emitting element for application ofUV radiation (which may also be indicated as “anti-fouling light”) (to apart of an external surface of the object), wherein the UV emittingelement especially comprises one or more light sources, even moreespecially one or more solid state light sources, and is configured toirradiate with said UV radiation (during an irradiation stage) one ormore of (i) a (said) part of said external surface and (ii) wateradjacent to said part of said external surface, wherein the object isespecially selected from the group consisting of a vessel and aninfrastructural object.

In yet a further aspect, the invention also provides the anti-biofoulingsystem per se, i.e. an anti-biofouling system comprising an UV emittingelement for application of UV radiation (to a part of an externalsurface of the object), wherein the UV emitting element comprises one ormore light sources and is configured to irradiate with said UV radiation(during an irradiation stage) one or more of (i) said part of saidexternal surface and (ii) water adjacent to said part of said externalsurface. The invention is further especially explained with reference tothe bio-antifouling system in combination with the object.

In yet a further specific embodiment, the object further comprises awater switch, wherein the anti-biofouling system is configured toprovide said UV radiation to said part when the water switch is inphysical contact with the water, especially electrically conductivewater, such as sea water. The water switch is especially herein definedas an electrical switch which upon contact with the water may switch anelectrical device on or off, especially switch on. Hence, the waterswitch is especially an electrical water switch. The term “water switch”may also refer to a plurality of water switches. In general each waterswitch may functionally be coupled to a single light source or to asubset of light sources or to a UV emitting element or to a subset of UVemitting elements. Hence, in embodiments wherein the water switch is notin physical contact with water, the (respective) anti-biofouling systemmay not provide UV radiation. When the water switch is in physicalcontact with water, the (respective) anti-biofouling system may provideUV radiation (though in embodiments a control system may overrule this(temporarily)(see also below)).

A further advantage of a water switch may e.g. be in combination with acontrol system. Such control system may e.g. instruct the UV emittingelement to provide UV radiation. The water switch may then be anadditional safety valve, only actually allowing providing UV radiationwhen the water switch is in physical contact with water. Hence, in afurther aspect the invention provides an object that during use is atleast partly submerged in water, the object further comprising ananti-biofouling system comprising an UV emitting element, wherein the UVemitting element comprises one or more light sources and is configuredto irradiate with UV radiation during an irradiation stage one or moreof (i) a part of a (said) external surface of said object and (ii) wateradjacent to said part of said external surface, wherein the object isselected from the group consisting of a vessel and an infrastructuralobject, wherein the object further comprises a water switch, wherein theanti-biofouling system is configured to provide said UV radiation tosaid part in dependence of the water switch being in physical contactwith the water.

Especially e.g. the part and the water switch may be configured at asame height. In this way, when the part is submerged, the water switchmay switch on the UV emitting element, whereas when the part is notsubmerged, the water switch may switch of the UV emitting element. Withsuch bio-antifouling system the UV radiation may be minimized insituations or applications wherein UV radiation may be considered risky,whereas in situations or applications wherein the application of UVradiation is less risky or not risky, the UV radiation may be applied.As indicated above, the anti-biofouling system may comprises a pluralityof light sources, a plurality of radiation escape surfaces, and aplurality of said parts, wherein the plurality of light sources areconfigured to provide said UV radiation via said plurality of radiationescape surfaces to said plurality of parts, and wherein said pluralityof parts are configured at different heights of the object. Further,especially the anti-biofouling system may further comprise a pluralityof said water switches, configured at the heights of the plurality ofparts, and wherein the anti-biofouling system is configured to providesaid UV radiation to said parts when the respective water switches arein physical contact with the (electrically conductive) water. Hence, inthis way, substantially irrespective of the draft or the water (line),the desired safety can be guaranteed as only UV radiation will beprovided to the external surface parts that are below the water (line).Hence, the object may include a plurality of UV emitting elements,configured at different heights. Further, the object may comprise aplurality of water switches, also configured at different heights andconfigured to switch on the light source(s) of the respective UVemitting elements at substantially the same height as the waterswitches. In an embodiment, the object may comprise a plurality of UVemitting elements, applied at different heights of the external surface,and a plurality of water switches arranged at different heights, whereinthe UV-emitting elements and water switches are functionally connected,wherein the heights are defined relative to the external surface duringuse of the object, wherein the anti-biofouling system is configured toprovide said UV radiation with one or more UV emitting elements independence of the related one or more water-switches being in physicalcontact with electrically conductive water.

When using a water switch, such water switch may be configured close tothe radiation escape surface, but configured higher, such as at least 10cm higher, especially at least 20 cm higher, such as in the range of10-100 cm higher, like 20-50 cm higher (relative to the object duringuse) than said surface. In this way, the UV radiation may only begenerated when the water switch, and thus the radiation escape surface,is below the water (line) (see further also below).

In this way, it may thus be guaranteed that UV light will only beemitted at least e.g. 50 cm below the waterline; which is sufficient toabsorb a substantial part of the light. Depending on the absoluteintensity of the ‘on’ level, a lower or higher value than 50 cm may bedesigned, such as to achieve an inherently safe system.

The water switch may in an embodiment be configured to close anelectronic circuit when physically being in contact with (electrically)conductive water. In an alternative or additional embodiment, the waterswitch may include a sensor configured to sense water and configured toprovide a sensor signal when the sensor is physically in contact withwater.

Especially, the object, or the anti-biofouling system, may furthercomprise a control system. Hence, the object comprises such comprisessuch control system, which may optionally be integrated in theanti-biofouling system, or elsewhere in the object. In a specificembodiment, the control system is especially configured to control saidUV radiation as function of input information comprising information ofone or more of (i) a location of the object, (ii) movement of theobject, (iii) a distance (d) of the object to a second object, and (iv)a position of the part of the external surface relative to the water.Hence, especially the anti-biofouling system is configured to controlsaid UV radiation as function of input information comprisinginformation of a human UV radiation exposure risk.

With such bio-antifouling system the UV radiation may be minimized insituations or applications wherein UV radiation may be considered risky,whereas in situations or applications wherein the application of UVradiation is less risky or not risky, the UV radiation may be applied.For instance, the biofouling unit may be configured to provide UVradiation only at open sea, or when the object is moving at cruisespeed, or when no people are detected in the vicinity of the object orbio-antifouling system, or when the relevant part of the bio-antifoulingsystem is below the water line (see further also below).

Herein, the phrase “object that during use is at least partly submergedin water” especially refers to objects such as vessels andinfrastructural objects that have aquatic applications. Hence, duringuse such object will be in general in contact with the water, like avessel in the sea, a lake, a canal, a river, or another waterway, etc.The term “vessel” may e.g. refer to e.g. a boat or a ship, etc., such asa sail boat, a tanker, a cruise ship, a yacht, a ferry, a submarine,etc. etc. The term “infrastructural object” may especially refer toaquatic applications that are in general arranged substantiallystationary, such as a dam, a sluice, a pontoon, an oilrig, etc. etc. Theterm “infrastructural object” may also refer pipes (for e.g. pumping upocean water to e.g. a power plant), and other parts of(hydro-electrical) power plants, such as cooling systems, turbines, etc.The term “external surface” especially refers to the surface that may bein physical contact with water. In the case of pipes this may apply toone or more of the internal pipe surface and the external pipe surface.Hence, instead of the term “external surface” also the term “foulingsurface” may be applied. Further, in such embodiments the term “waterline” may also refer to e.g. filling level. Especially, the object is anobject configured for marine applications, i.e. application in or nearto a sea or an ocean. Such objects are during their use at leasttemporarily, or substantially always, at least partly in contact withthe water. The object may be at least partly below the water (line)during use, or may substantially be all of its time below the water(line), such as for submarine applications.

Due to this contact with the water, biofouling may occur, with the aboveindicated disadvantages. Biofouling will occur at the surface of anexternal surface (“surface) of such object. The surface of an (elementof the) object to be protected may comprise steel, but may optionallyalso comprise another material, such as e.g. selected from the groupconsisting of wood, polyester, composite, aluminium, rubber, hypalon,PVC, glass fiber, etc. Hence, instead of a steel hull, the hull may alsobe a PVC hull or a polyester hull, etc. Instead of steel, also anotheriron material, such as an (other) iron alloys may be used

Herein, the term “fouling” or “biofouling” or “biological fouling” areinterchangebly used. Above, some examples of fouling are provided.Biofouling may occur on any surface in water, or close to water andbeing temporarily exposed to water (or another electrically conductiveaqueous liquid). On such surface biofouling may occur when the elementis in, or near water, such as (just) above the water line (like e.g. dueto splashing water, such as for instance due to a bow wave). Between thetropics, biofouling may occur within hours. Even at moderatetemperatures, the first (stages of) fouling will occur within hours; asa first (molecular) level of sugars and bacteria.

The anti-biofouling system comprises at least an UV emitting element.Further, the anti-biofouling system may comprise a control system (seealso below), an electrical energy supply, such as a local energyharvesting system (see also below), etc.

The term “anti-biofouling system” may also refer to a plurality of suchsystems, optionally functionally coupled to each other, such as e.g.controlled via a single control system. Further, the anti-biofoulingsystem may comprise a plurality of such UV emitting elements. Herein,the term “UV emitting element” may (thus) refer to a plurality of UVemitting elements. For instance, in an embodiment a plurality of UVemitting elements may be associated to an external surface of theobject, such as a hull, or may be comprised by such surface (see alsobelow), whereas e.g. a control system may be configured somewhere withinthe object, such as in a control room or wheel house of a vessel.

The surface or area on which fouling may be generated is herein alsoindicated as fouling surface. It may e.g. be the hull of a ship and/oran emission surface of an optical medium (see also below). To this end,the UV emitting element provides UV radiation (anti-fouling light) thatis applied to prevent formation of biofouling and/or to removebiofouling. This UV radiation (anti-fouling light) especially at leastcomprises UV radiation (also indicated as “UV light”). Hence, the UVemitting element is especially configured to provide UV radiation.Thereto, the UV emitting element comprises a light source. The term“light source” may also relate to a plurality of light sources, such as2-512, such as 2-20 (solid state) LED light sources, though many morelight sources may also be applied. Hence, the term LED may also refer toa plurality of LEDs. Especially, the UV emitting element may comprise aplurality of light sources. Hence, as indicated above, the UV emittingelement comprises one or more (solid state) state light sources. TheLEDs may be (OLEDs or) solid state LEDs (or a combination of theseLEDs). Especially, the light source comprises solid state LEDs. Hence,especially, the light source comprises a UV LED configured to provideone or more of UV-A and UVC light (see also below). UV-A may be used toimpair cell walls, whereas UVC may be used to impair DNA. Hence, thelight source is especially configured to provide the UV radiation.Herein, the term “light source” especially refers to a solid state lightsource.

Ultraviolet (UV) is that part of electromagnetic light bounded by thelower wavelength extreme of the visible spectrum and the X-ray radiationband. The spectral range of UV light is, by definition between about 100and 400 nm (1 nm=10⁻⁹ m) and is invisible to human eyes. Using the CIEclassification the UV spectrum is subdivided into three bands: UVA(long-wave) from 315 to 400 nm; UVB (medium-wave) from 280 to 315 nm;and UVC (short-wave) from 100 to 280 nm. In reality many photobiologistsoften speak of skin effects resulting from UV exposure as the weightedeffect of wavelength above and below 320 nm, hence offering analternative definition.

A strong germicidal effect is provided by the light in the short-waveUVC band. In addition erythema (reddening of the skin) andconjunctivitis (inflammation of the mucous membranes of the eye) canalso be caused by this form of light. Because of this, when germicidalUV-light lamps are used, it is important to design systems to excludeUVC leakage and so avoid these effects. In case of immersed lightsources, absorption of UV light by water may be strong enough that UVCleaking is no problem for humans above the liquid surface. Hence, in anembodiment the UV radiation (anti-fouling light) comprises UVC light. Inyet another embodiment, the UV radation comprises radiation selectedfrom a wavelength range of 100-300 nm, especially 200-300 nm, such as230-300 nm. Hence, the UV radation may especially be selected from UVCand other UV radiation up to a wavelength of about 300 nm. Good resultsare obtained with wavelengths within the range of 100-300 nm, such as200-300 nm. Especially, the UV radiation has a wavelenght below 380 nm.

As indicated above, the UV emitting element is configured to irradiatewith said UV radiation (during an irradiation stage) one or more of (i)said part of said external surface and (ii) water adjacent to said partof said external surface. The term “part” refers to part of the externalsurface of an object, such as e.g. a hull or a sluice (door). Howeverthe term “part” may also refer to substantially the entire externalsurface, such as the external surface of the hull or sluice. Especially,the external surface may comprise a plurality of parts, which may beirradiated with the UV light of one or more light sources, or which maybe irradiated with the UV radiation of one or more UV emitting elements.Each UV emitting element may irradiate one or more parts. Further, theremay optionally be parts that receive UV radiation of two or more UVemitting elements.

In general, there may be distinguished between two main embodiments. Oneof the embodiments includes the part of the external surface beingirradiated with the UV radiation with between the light source and UVemitting element water (or air when above the water line), such as seawater, at least during the irradiation stage. In such embodiment, thepart is especially comprised by the “original” external surface of theobject. However, in yet another embodiment, the “original” externalsurface may be extended with a module, especially a relatively flatmodule, that is attached to the “original” external surface of theobject (such as the hull of a vessel), whereby the module itself formsin fact the external surface. For instance, such module may beassociated to the hull of a vessel, whereby the module forms (at leastpart of) the external surface. In both embodiments the UV emittingelement especially comprises a radiating exit surface (see further alsobelow). However, especially in the latter embodiment wherein the UVemitting element may provide part of said external surface, suchradiation escape surface may provide the part (as the first part and theradiation escape surface may essentially coincide; especially may be thesame surface).

Hence, in an embodiment the UV emitting element is attached to saidexternal surface. In yet a further specific embodiment the radiationescape surface of the anti-biofouling system is configured as part ofsaid external surface. Hence, in some of the embodiments the object maycomprise a vessel comprising a hull, and the UV emitting element isattached to said hull. The term “radiation escape surface” may alsorefer to a plurality of radiation escape surfaces (see also below).

In both general embodiments, the UV emitting element is configured toirradiate with said UV radiation (during an irradiation stage) wateradjacent to said part of said external surface. In the embodimentswherein the module itself forms in fact the external surface, the UVemitting element is at least configured to irradiate with said UVradiation (during an irradiation stage) said part of said externalsurface, as it is in fact part of said external surface, and optionallyalso water adjacent to said part of said external surface. Hereby,biofouling may be prevented and/or reduced.

In an embodiment, a significant amount of a protected surface to be keptclean from fouling, preferably the entire protected surface, e.g. thehull of a ship, may be covered with a layer that emits germicidal light(“anti-fouling light”), in particular UV light.

In yet another embodiment, the UV radiation (anti-fouling light) may beprovided to the surface to be protected via a waveguide, such as afiber.

Hence, in an embodiment the anti-fouling lighting system may comprise anoptical medium, wherein the optical medium comprises a waveguide, suchas an optical fiber, configured to provide said UV radiation(anti-fouling light) to the fouling surface. The surface of e.g. thewaveguide from which the UV radiation (anti-fouling light) escapes isherein also indicated as emission surface. In general, this part of thewaveguide may at least temporarily be submerged. Due to the UV radiation(anti-fouling light) escaping from the emission surface, an element ofthe object that is during use at least temporarily exposed to the liquid(such as seawater), may be irradiated, and thereby anti-fouled. However,the emission surface per se may also be anti-fouled. This effect is usedin some of the embodiments of the UV emitting element comprising anoptical medium described below.

Embodiments with optical media are also described in WO2014188347. Theembodiments in WO2014188347 are herein also incorporated by reference asthey are combinable with the control unit and/or water switch, and otherembodiments, described herein.

As indicated above, the UV emitting element may especially comprise a UVradiation escape surface. Hence, in a specific embodiment the UVemitting element comprises a UV radiation escape surface, with the UVemitting element especially being configured to provide said UVradiation downstream from said UV radiation escape surface of said UVemitting element. Such UV radiation escape surface may be an opticalwindow through which the radiation escapes from the UV emitting element.Alternatively or additionally, the UV radiation escape surface may bethe surface of a waveguide. Hence, UV radiation may be coupled in the UVemitting element into the waveguide, and escape from the element via a(part of a) face of the waveguide. As also indicated above, inembodiments the radiation escape surface may optionally be configured aspart of the external surface of the object.

The terms “upstream” and “downstream” relate to an arrangement of itemsor features relative to the propagation of the light from a lightgenerating means (here the especially the first light source), whereinrelative to a first position within a beam of light from the lightgenerating means, a second position in the beam of light closer to thelight generating means is “upstream”, and a third position within thebeam of light further away from the light generating means is“downstream”.

Especially, the (solid state) light source is at least controllablebetween a first UV radiation level and a second UV radiation level,wherein the first UV radiation level is larger than the second UVradiation level (and wherein the second UV radiation level is smallerthan the first radiation level or may even be zero). Hence, in anembodiment the light source can be switched off and can be switched on(during a radiation stage). Further, optionally also the intensity ofthe UV radiation may be controlled between these two stages, such as astepwise or continuous UV radiation intensity control. Hence, the lightsource is especially controllable (and thus its UV radiation intensityis).

As indicated above, the control system is especially configured tocontrol said UV radiation as function of input information comprisinginformation of one or more of (i) a location of the object, (ii)movement of the object, (iii) a distance (d) of the object to a secondobject, and (iv) a position of the part of the external surface relativeto the water.

In an embodiment, wherein the control system may be configured tocontrol the UV emitting element to the first UV radiation level when thelocation of the object complies with a first predetermined location, andto the second UV radiation level when the location of the objectcomplies with a second predetermined location. For instance, based onlocation date, such as with the aid of satellite navigation, thelocation of the object can be know and the control system can thendetermine whether such location has an enhanced risk for UV exposure toe.g. humans, such as in a harbor, or a reduced (or no) risk, such as ona river or on the sea. The term “predetermined location” may also referto a plurality of predetermined locations, such as geographical areas,like “open sea”, “more than 1 mile offshore”, etc.

In yet a further embodiment, the control system may be configured tocontrol the UV emitting element to the first UV radiation level when theobject has a velocity of at least a predetermined minimum velocity, andto the second UV radiation level when the velocity of the objects isbelow said predetermined minimum velocity. For instance, when thevelocity of the object is zero, it is likely that the risk of UVexposure to humans may be higher, because the object may e.g. be inmaintenance, or a vessel may be in a harbor or people may walk over asluice, etc. etc. However, when the velocity is non-zero, or over acertain threshold, such risks will substantially be reduced as ingeneral people will then not be in the vicinity of the relevant part(s)of the external surface (or only for short periods of time), which willin general be just above the water (line), at the waterline and below.

In yet a further embodiment, the control system may be configured tocontrol the UV emitting element to the first UV radiation level when thedistance (d) of the object to the second object meets at least apredefined threshold value, and to the second UV radiation level whenthe distance (d) of the object to the second object is below thepredefined threshold value. The second object may be a human or anyother living or non living object, in general having a volume of atleast about 1 dm³. In general, this embodiment may include a sensor,configured to sense other objects. Hence, the object or in an embodimentthe anti-biofouling system (or both), may further comprise a sensorconfigured to sense one or more of (i) the second object and (ii) amovement of the second object and configured to generate a correspondingsensor signal, and wherein the control system is configured to controlsaid UV radiation as function of said sensor signal. Hence, e.g. at opensea, or on a river, no second object may (often) be sensed, whereas e.g.in a harbor people may be sensed. In the former situation, the UVradiation may be applied; in the latter situation the UV radiation maybe reduced or switched off. The sensor may e.g. include a thermal sensoror a motion sensor, etc. Further, the term “sensor” may also refer to aplurality of sensors, of which optionally two or more may be configuredto sense different properties. Hence, in embodiments the sensor mayinclude a motion sensor, such as configured to sense a human.

In an embodiment, the control system comprises a plurality of controlsystems. For instance, the vessel may comprise a control system, asmaster control system, with each anti-biofouling system comprising aslave control system. Optionally, the control system may be configuredexternal form the object, i.e. remote from the object. In a specificembodiment, a master control system, remote from the object, controlsthe slave control system comprised by the object, (such as theanti-biofouling system). Hence, for instance the (master) control systemmay be far away; or not on the vessel, but ashore, such as in a controlroom of a shipping company. Such master control system may be configuredto control anti-biofouling systems of a plurality of objects.

A relative simple way to reduce the risk of undesired UV radiationexposure of humans may be apply UV radiation only below the water(line). Hence, in an embodiment the control system is configured tocontrol the UV emitting element to the first UV radiation level when oneor more of the part and the UV radiation escape surface are below thewater (line), and to the second UV radiation level when one or more ofthe part and the UV radiation escape surface are above the water (line).This may include the use of one or more of (i) a sensor configured tosense the water (line), and (ii) information about loading. Basedthereon, the control system may decide whether or not the UV radiationcan be applied or will be applied substantially only to the part of theexternal surface that is below the water (line). Note that in thisembodiment there may still be a plurality of variants as the radiationmay in general then only be applied when the part is below the water(line), but optionally the UV radiation escape surface may be above thewater (line), or also below the water (line). In the latter variant,risk may even be further minimized. Hence, especially the control systemis configured to control the UV emitting element to the first UVradiation level when the UV radiation escape surface is below the water(line) and to the second UV radiation level when the UV radiation escapesurface is above the water (line). Alternatively or additionally,especially in an embodiment the control system is configured to controlthe UV emitting element to the first UV radiation level when the part(and the UV radiation escape surface is below the water (i.e. especiallythe water line), and to the second UV radiation level when the part isabove the water (i.e. especially the water line). When using a sensorconfigured to sense the water, such sensor may be configured close tothe radiation escape surface, but configured higher, such as at least 10cm higher, especially at least 20 cm higher, such as in the range of10-100 cm higher, like 20-50 cm higher (relative to the object duringuse) than said surface. In this way, the UV radiation may only begenerated when the sensor, and thus the radiation escape surface, isbelow the water (line) (see further also below). In this way, it maythus be guaranteed that UV light will only be emitted at least e.g. 50cm below the waterline; which is sufficient to absorb a substantial partof the light. Depending on the absolute intensity of the ‘on’ level, alower or higher value than 50 cm may be designed, such as to achieve aninherently safe system.

As indicated above, the object or the anti-biofouling system maycomprise a plurality of radiation escape surfaces. In embodiments thismay refer to a plurality of anti-biofouling systems. However,alternatively or additionally, in embodiments this may refer to ananti-biofouling system comprising a plurality of UV radiation emittingelements. Such anti-biofouling system may thus especially include aplurality of light sources for providing UV radiation. However,alternatively or additionally, in embodiments this may (also) refer toan UV emitting element comprising a plurality of light sourcesconfigured to provide the UV radiation. Note that an UV emitting elementwith a single UV radiation escape surface may (still) include aplurality of light sources.

Especially, when the UV emitting element comprises a plurality of lightsources and a plurality of UV radiation escape surfaces, especially witheach of such surface addressed by one more light sources, and/or whenthe bio-fouling system comprises a plurality of UV emitting elements, bya control of the light sources it is possible to address different partsof the external surface independently. Hence, by arranging the differentUV radiation escape surfaces at different heights of the object (withthe height especially defined during use of the object), it is possibleto substantially only irradiate with UV radiation only those parts forwhich applies that one or more of the part and the UV radiation escapesurface are below the water (line).

Hence, in a specific embodiment the anti-biofouling system comprises aplurality of light sources, a plurality of radiation escape surfaces,and a plurality of said parts, wherein the plurality of light sourcesare configured to provide said UV radiation via said plurality ofradiation escape surfaces to said plurality of parts, and wherein saidplurality of parts are configured at different heights of the object.Especially, the control system may be configured to control the (solidstate) light sources individually as function of said input information.For instance, in a specific embodiment the control system may beconfigured to control the light sources individually as function of thepositions of the parts of the external surface relative to the water(i.e. the water line). For instance, the anti-bio fouling system maycomprise a sensor or another element to sense water in the vicinity ofthe relevant radiation escape surface and/or part. It is noted againthat in some embodiments the radiation escape surface may comprise thepart. Alternatively or additionally, the input information comprisinginformation of the position of the external surface relative to thewater is based on a loading of the vessel. Also in this way, the controlsystem may control the UV radiation, e.g. as function of e.g. thepositions of the parts of the external surface relative to the water.Alternatively or additionally, the control system may control the UVradiation, e.g. as function of e.g. the positions of UV radiation escapesurfaces relative to the water. However, the control system may also beconfigured to calculate the draft (draught) of the object, especiallywhen the object is a vessel, and/or receive from an external sourceinformation about the draft. Hence, in a further embodiment the inputinformation comprises a calculated draft of the object. In otherembodiments, wherein the object is not a vessel, the input informationcomprising information of the position of the external surface relativeto the water may be based on a water line (or water level) relative tothe infrastructural object.

For vessels, waves might make for a rapidly changing water line and forinfrastructure objects, optionally the tides (or a filling level) maymake a difference in the water line. Hence, especially the control unitand the optional sensor are configured (to be able) to follow thesechanges. For instance, the sensor may be configured to sensecontinuously, or periodically with a frequency able to follow suchchanges.

In yet a further embodiment, the object or the anti-biofouling systemmay further comprise a local energy harvesting system configured toharvest electrical energy and to provide said energy to saidanti-biofouling system. In this way, e.g. the anti-biofouling system maybe substantially independent of the mains, even e.g. a local mains on avessel. In a specific embodiment, the local energy harvesting system maybe comprised by said anti-biofouling system. In an embodiment, the localenergy harvesting system is selected from the group consisting of asolar cell, a turbine operating in water, a piezoelectric elementoperating on a pressure of waves, etc. etc.

For instance, in an embodiment solar cells may be configured at thefreeboard, and the UV emitting elements may be configured below thefreeboard.

In yet another embodiment, the turbine and/or element that can deriveenergy from flow of water or pressure changes due to water movements,etc., as well as the UV emitting element are configured below thefreeboard.

The term “local energy harvesting system” may also refer to a pluralityof such local energy harvesting systems. Each of such local harvestingsystem may functionally be coupled with one or more anti-biofoulingsystems. Alternatively, each of such local harvesting system mayfunctionally be coupled with one or more UV emitting elements.Especially, as also indicated above in relation to the water switches,especially the local energy harvesting systems may be configured at theheights of a plurality of parts or the UV radiation escape surface. Inthis way, only when the part and/or the UV radiation escape surface issubmerged, especially when at least the UV radation escape surface issubmerged, energy can be harvested. In this way, automatically the UVradation may only be switched on when the conditions are relativelysafe.

In yet another embodiment, the energy can be harvested from water by theuse of a sacrificial electrode. Especially, such a sacrificial electrodemay be configured at the height of the part or of the UV radiationescape surface. In an embodiment, the local energy harvesting systemcomprises (i) a sacrificial electrode in electrical connection with afirst electrode of the light source, and (ii) a second energy systemelectrode in electrical connection with a second electrode of the lightsource, wherein the energy system is configured to provide electricalpower to said anti-biofouling system when the sacrificial electrode andthe second energy system electrode are in electical contact with the(electrically conductive) water. The term “sacrificial electrode” mayalso relate to a plurality of sacrificial electrodes.

Hence, in a further embodiment the sacrificial electrode is comprised bythe water switch, wherein the anti-biofouling system is configured toprovide said UV radiation to said part in dependence of the sacrificialelectrode being in physical contact with the water. Hence, the waterswitch and energy harvesting system may be at least partially beingintegrated, with the sacrificial electrode being configured assacrificial electrode and especially as necessary element in the waterswitch which may provide a closed electrical circuit only when the thesacrificial electrode is in physical contact with water.

In a specific embodiment, the sacrificial electrode comprises one ormore of zinc and magnesium. The sacrificial electrode will be inelectrical connection with a first pole or electrode or terminal of thelight source, UV emitting device, anti-biofouling system, respectively,and a second electrode (also indicated as “second energy systemelectrode”) of the local energy harvesting system will be in electricalconnection with a second pole or electrode or terminal of the lightsource, UV emitting device, anti-biofouling system, respectively.

In a further embodiment, the second energy system electrode comprisessteel iron, such as steel. However, other materials may also be applied,like especially one or more of carbon, graphite, coke, platinum, millscale on steel, high silicon cast iron, copper, brass, bronze, lead, andcast iron (not graphitized), instead of or in addition to e.g. steel.The phrase “wherein the sacrificial electrode comprises one or more ofzinc and magnesium” may also refer to sacrificial electrodes comprisingan alloy comprising zinc and/or magnesium. However, the sacrificialelectrode may also substantially consist of zinc and/or magnesium. Othermaterials may also be applied, such as some sorts of aluminum oraluminum alloys.

For example, one copper electrode and one zink electrode, each connectedto a different terminal of the LED and both submerged in water, maygenerate a voltage (and thus current). Once above water, the generationof current will automatically and instantly stop.

In yet further embodiments the UV radiation may be accompanied bywarning information. For instance, when the UV radiation is switched on,especially above the water (line), one or more of a sound signal and alight signal may be provided. The sound signal and/or light signal mayinclude warning information, such as spoken text, projected text, or aconfiguration of light that contains information (similar to a display).

In a specific embodiment, the UV emitting element comprises aluminescent material configured to absorb part of the UV radiation andconvert into visible luminescent material light (i.e. visible lightgenerated by the luminescent material upon excitation with the UVradiation), wherein the light source and said luminescent material areconfigured to provide said visible luminescent material light emanatingin a direction away from the external surface. Optionally, theanti-biofouling system is configured to provide said luminescentmaterial light in a pulsed way. Hence, in this way, a person at adistance from the object (and thus external from the object) mayperceive the luminescence, e.g. a red blinking light.

Alternatively or additionally, the UV emitting element comprises asecond light source configured to provide visible second light sourcelight of which at least part emanates in a direction away from theexternal surface. Again, optionally the anti-biofouling system may beconfigured to provide said visible second light source light in a pulsedway. Hence, in this way, a person at a distance from the object (andthus external from the object) may perceive the visible second lightsource light, e.g. a red blinking light.

In yet a further embodiment, the anti-biofouling system may further beconfigured to provide visible light emanating as a light beam in adirection away from the external surface, wherein the light beam has across-section having the shape of a warning sign. This visible light mayin embodiments be provided by one or more of the second light source andthe luminescent material. Hence, the second light sources may beconfigured in a warning signal configuration, which may especially bevisible when the second light sources are switched on.

Yet in further embodiments the anti-biofouling system may furthercomprise a sensor configured to provide a sensor signal indicative forone or more of (i) the sensor being in physical contact with the waterand (ii) the part being in physical contact with the water, and acontrol system, wherein the control system is configured to provide saidUV radiation as function of said sensor signal.

Further, one may also take into account the fact that some parts of theobject may substantially always be below the water (line). In anembodiment, wherein the object comprises a vessel, the UV radiationescape surface may be configured to the external surface of the objectat a position which is permanent under the water (line) during use ofthe object. For instance, this may be the load line of the vessel atzero load. However, this embodiment may also be applied toinfrastructural object. One may however have sometimes to take intoaccount lower levels in the summer (and higher levels in the winter).Note that the fact that the UV radiation escape surface maysubstantially always below the water (line), this does not imply thatthe entire anti-biofouling system has to be below the water (line).

A further precautionary measure that may be taken may be related to thedirection of the UV radiation. In a specific embodiment the UV emittingelement is configured to provide at least 80%, such as at least 90%, oreven substantially all, of the power of the UV radiation in a directionwithin an angle of 0-90° such as within an angle of 0-45° from aperpendicular to the earth's surface and in a direction below theobject, relative to the object during its use.

The anti-biofouling system is especially configured to provide UVradiation to the part of the object or to water adjacent to this part.This especially implies that during an irradiation stage the UVradiation is applied. Hence, there may optionally also be periodswherein no UV radiation is applied at al. This may (thus) not only bedue to e.g. a control system switching of one or more of the UV emittingelements, but may e.g. also be due to predefined settings such as dayand night or water temperature, etc. For instance, in an embodiment theUV radiation is applied in a pulsed way.

Hence, in a specific embodiment or aspect, the anti-biofouling system isconfigured for preventing or reducing biofouling on a fouling surface ofan object, that during use is at least temporarily exposed to water, byproviding an anti-fouling light (i.e. UV radiation) to said foulingsurface or water adjacent thereto, the anti-fouling lighting systemcomprising (i) a lighting module comprising (i) a light sourceconfigured to generate said anti-fouling light; and (ii) a controlsystem configured to control an intensity of the anti-fouling light asfunction of one or more of (i) a feedback signal related to a biofoulingrisk and (ii) a timer for time-based varying the intensity of theanti-fouling light. Especially, the anti-biofouling system may beconfigured to provide said anti-fouling light via an optical medium tosaid fouling surface, wherein the lighting module further comprises (ii)said optical medium configured to receive at least part of the UVradiation (anti-fouling light), the optical medium comprising anemission surface configured to provide at least part of said UVradiation (anti-fouling light). Further, especially the optical mediumcomprises one or more of a waveguide and an optical fiber, and whereinthe UV radiation (anti-fouling light) especially comprises one or moreof UVB and UVC light. These waveguides and optical media are hereinfurther not discussed in detail.

The optical medium may also be provided as a (silicone) foil forapplying to the protected surface, the foil comprising at least onelight source for generating anti-fouling light and a sheet-like opticalmedium for distributing the UV radiation across the foil. In embodimentsthe foil has a thickness in an order of magnitude of a couple ofmillimeters to a few centimeters, such as 0.1-5 cm, like 0.2-2 cm. Inembodiments, the foil is not substantially limited in any directionperpendicular to the thickness direction so as to provide substantiallylarge foil having sizes in the order of magnitude of tens or hundreds ofsquare meters. The foil may be substantially size-limited in twoorthogonal directions perpendicular to the thickness direction of thefoil, so as to provide an anti-fouling tile; in another embodiment thefoil is substantially size-limited in only one direction perpendicularto a thickness direction of the foil, so as to provide an elongatedstrip of anti-fouling foil. Hence, the optical medium, and even also thelighting module, may be provided as tile or as strip. The tile or stripmay comprise a (silicone) foil.

In an embodiment the lighting module comprises a two-dimensional grid oflight sources for generating UV radiation and the optical medium isarranged to distribute at least part of the UV radiation from thetwo-dimensional grid of light sources across the optical medium so as toprovide a two-dimensional distribution of UV radiation exiting the lightemitting surface of the light module. The two-dimensional grid of lightsources may be arranged in a chicken-wire structure, a close-packedstructure, a rows/columns structure, or any other suitable regular orirregular structure. The physical distance between neigboring lightsources in the grid may be fixed across the grid or may vary, forexample as a function of light output power required to provide theanti-fouling effect or as function of the location of the lightingmodule on the protected surface (e.g location on the hull of a ship).Advantages of providing a two-dimensional grid of light sources includethat the UV radiation may be generated close to the areas to beprotected with UV radiation illumination, and that it reduces losses inthe optical medium or light guide and that it is increasing homogeneityof the light distribution. Preferably, the UV radiation is generallyhomogeneously distributed across the emission surface; this reduces oreven prevents under-illuminated areas, where fouling may otherwise takeplace, while at the same time reducing or preventing energy waste byover-illumination of other areas with more light than needed foranti-fouling. In an embodiment, the grid is comprised in the opticalmedium. In yet another embodiment, the grid may be comprised by a(silicone) foil.

Further, in an embodiment the optical medium may be disposed proximate(including optionally attached to) to the protected surface and coupledto receive the ultraviolet light, wherein the optical medium has athickness direction perpendicular to the protected surface, wherein twoorthogonal directions of the optical medium orthogonal to the thicknessdirection are parallel to the protected surface, wherein the opticalmedium is configured to provide a propagation path of the ultravioletlight such that the ultraviolet light travels within the optical mediumin at least one of the two orthogonal directions orthogonal to thethickness direction, and such that, at points along a surface of theoptical medium, respective portions of the ultraviolet light escape theoptical medium.

In a further aspect, the invention also provides a method ofanti-(bio)fouling (a part of) an external surface of an object that isduring use at least temporarily exposed to water, the method comprising:providing the anti-biofouling system as defined herein to the object,generating the UV radiation (during use of the object), optionally asfunction of one or more of (i) a feedback signal (such as related tobiofouling risk and/or a human UV radiation exposure risk), and (ii) atimer for (periodically) varying the intensity of the UV radiation(anti-fouling light), and providing said UV radiation (during anirradiation stage) to (the part of) the external surface. Such feedbacksignal may be provided by the sensor.

In yet a further aspect, the invention also provides a method ofproviding an anti-biofouling system to an object, that during use is atleast temporarily exposed to water, the method comprising providing,such as integrating in the object and/or attaching to an externalsurface, the anti-biofouling system to the object, such as a vessel,with the UV emitting element configured to provide said UV radiation toone or more of a part of an external surface of the object and water(being) adjacent to said part (during use). Especially, the UV emittingelement is attached to the external surface, or may even be configuredas (first) part of the external surface.

The terms “visible”, “visible light” or “visible emission” refer tolight having a wavelength in the range of about 380-780 nm. Especially,the visible light has a wavelenght of more than 380 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIGS. 1a-1c schematically depict some general aspects;

FIGS. 2a-2f schematically depict some embodiments and variants;

FIGS. 3a-3b schematically depict some further embodiments and variants;

FIGS. 4a-4e schematically depict some further embodiments and variants;and

FIGS. 5a-5c schematically depict some further embodiments and variants.

The drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1a-1b schematically depict embodiments of an object 10 that duringuse is at least partly submerged in water 2, see the water line 13. Theobject 10, such as a vessel or a sluice, see also below, furthercomprises an anti-biofouling system 200 comprising an UV emittingelement 210, especially for application of UV radiation 221 to a part111 of an external surface 11 of the object 10, such as a hull or partor a hull. Here, two embodiments are shown wherein the anti-biofoulingsystem 200, or more especially the UV emitting element 210 is part of anouter surface, and thereby forms in fact part of the outer surface (FIG.1a ) or wherein the UV emitting element 210 is configured to irradiatethe outer surface and does not necessarily form part of an outersurface, such as a hull of a ship (FIG. 1b ). For instance, the object10 is selected from the group consisting of a vessel 1 and aninfrastructural object 15 (see also below).

The UV emitting element 210 comprises one or more light sources 220 andmay thus especially be configured to irradiate with said UV radiation221 during an irradiation stage one or more of (i) said part 111 of saidexternal surface 11 and (ii) water adjacent to said part 111 of saidexternal surface 11. The former variant applies especially theembodiment of FIG. 1b , and the latter embodiment especially applies toboth embodiments of FIGS. 1a-1b . Note however that when an externalsurface of the UV emitting element 210 is configured as external surfaceof the object 10, of course the part 111 is irradiated per se with theUV radiation 21.

Hence, the UV emitting element 210 comprises a UV radiation escapesurface 230 and the UV emitting element 210 is configured to providesaid UV radiation 221 downstream from said UV radiation escape surface230 of said UV emitting element 210.

Especially, the light source 220 is at least controllable between afirst UV radiation level and a second UV radiation level, wherein thefirst UV radiation level is larger than the second UV radiation level(and wherein the second UV radiation level is smaller than the firstradiation level (including e.g. zero).

In a specific embodiment, the object 10 further comprises a controlsystem 300 configured to control said UV radiation 221 as function ofinput information comprising information of one or more of (i) alocation of the object 10, (ii) movement of the object 10, (iii) adistance d of the object 10 to a second object 20, and (iv) a positionof the part 111 of the external surface 11 relative to the water. Thisis further elucidated in amongst others FIGS. 2a -2 f.

As indicated above, the term “vessel”, indicated with reference 1, maye.g. refer to e.g. a boat or a ship (ref 10 a in FIG. 1c ), etc., suchas a sail boat, a tanker, a cruise ship, a yacht, a ferry, a submarine(ref. 10 d in FIG. 1c ), etc. etc., like schematically indicated in FIG.1c . The term “infrastructural object”, indicated with reference 15, mayespecially refer to aquatic applications that are in general arrangedsubstantially stationary, such as a dam/sluice (references 10 e/10 f inFIG. 1c ), a pontoon (ref. 10 c in FIG. 1c ), an oilrig (ref. 10 b inFIG. 1c ), etc. etc.

As indicated above, the object 10 may further comprises a control system300 configured to control said UV radiation 221 as function of inputinformation comprising information of one or more of (i) a location ofthe object 10, (ii) movement of the object 10, (iii) a distance (d) ofthe object 10 to a second object 20, and (iv) a position of the part 111of the external surface 11 relative to the water.

For instance, the location of the object, especially of a vessel 10 mayswitch on the UV radiation when on open water, whereas the UV emittingelement 210 may be switched off in a harbor. Satellite navigation maye.g. be used (for determination of the location of the object). Hence,in an embodiment the control system 300 is configured to control the UVemitting element 210 to the first UV radiation level when the locationof the object 10 complies with a first predetermined location, and tothe second UV radiation level when the location of the object 10complies with a second predetermined location.

Alternatively or additionally, the control system 300 may be configuredto control the UV emitting element 210 to the first UV radiation levelwhen the object 10 has a velocity of at least a predetermined minimumvelocity, and to the second UV radiation level when the velocity of theobjects 10 is below said predetermined minimum velocity. A low velocitymay indicate a higher likelihood of people in the vicinity of the UVemitting element 210 than a high velocity.

Alternatively or additionally, the control system 300 may be configuredto control the UV emitting element 210 to the first UV radiation levelwhen the distance d of the object 10 to the second object 20 meets atleast a predefined threshold value, and to the second UV radiation levelwhen the distance d of the object 10 to the second object 20 is belowthe predefined threshold value. This is schematically depicted in FIG. 2a.

For controlling the UV emitting element 210 as function of one or moreof the herein indicated parameters, the object 10 may further comprise asensor 310, see e.g. FIG. 2a , configured to sense one or more of (i) asecond object 20 and (ii) a movement of the second object (20) andconfigured to generate a corresponding sensor signal. The control system300 may especially be configured to control said UV radiation 221 asfunction of said sensor signal. The second object may be stationary ormoving. Further the second object may e.g. a human (see the example inFIG. 2a ), or non-moving, such as quay (see also FIG. 2a ). The sensormay optionally be comprised by the anti-bio-fouling system 200 (see e.g.FIG. 2 b.

FIG. 2b schematically depicts in more detail an embodiment of theanti-biofouling system 200, here by way of example including anintegrated control system 300 and an integrated sensor 310.

FIG. 2c schematically depicts an external surface 11 of an object 10,such as a vessel wall or a wall of an infrastructural object, with byway of example a plurality UV emitting elements 210 (here associated toa hull 21 of a vessel 1). Alternatively or additionally, a plurality offunctionally coupled or independently functioning anti-biofoulingsystems 200 may be applied.

For instance, assuming a single control system 300, which may e.g. be amaster control system with subordinated slave control systems (notdepicted), may e.g. be configured to control the UV emitting element 210to the first UV radiation level when one or more of the part 111 and theUV radiation escape surface 230 are below the water line 13, and to thesecond UV radiation level when one or more of the part 111 and the UVradiation escape surface 230 are above the water line 13. For instance,all UV emitting elements 210 below the water (line) may be switched on,while all above the water (line) may be switched off. Note that in theschematic drawing 2 c also one of the UV emitting elements 210 above thewater line 3 is switched, e.g. in the case that the control systemdecides that it is safe to switch such UV emitting elements 210 on. Useof an additional safeguard, such as a water switch may be used asalternative or additional control (see also below).

FIG. 2c also schematically depicts the embodiment wherein theanti-biofouling system 200 comprises a plurality of UV emitting elements210 (with a plurality of light sources), a plurality of radiation escapesurfaces 230, and a plurality of said parts 111, wherein the pluralityof light sources 220 are configured to provide said UV radiation 221 viasaid plurality of radiation escape surfaces 23 to said plurality ofparts 111, and wherein said plurality of parts 111 are configured atdifferent heights of the object 10, and wherein the control system 300is configured to control the light sources 220 individually as functionof said input information. For instance, in an embodiment the controlsystem 300 may be configured to control the light sources 220individually as function of the positions of the parts 111 of theexternal surface 11 relative to the water. In a first variant, the inputinformation comprising information of the position of the externalsurface 11 relative to the water is based on a loading of the vessel 1(schematically depicted in FIG. 2c ). In a second variant, the inputinformation comprising information of the position of the externalsurface 11 relative to the water is based on a water line relative tothe infrastructural object 15.

FIG. 2d schematically depicts an embodiment wherein alternatively oradditionally the object 10 further comprises a water switch 400, whereinthe anti-biofouling system 200 is configured to provide said UVradiation 221 to said part 111 in dependence of the water switch beingin physical contact with the water. In FIG. 2d , the water switch is incontact with the water. For instance, by electrical conductivity ofseawater, the electric circuit may be closed, by which the light source220 may provide UV radiation. An anti-biofouling system may comprise oneor more of such water switches 400. Optionally, the water switch 400 andlight source 220 may be part of a larger circuit with e.g. electronicsto amplify the signal, etc. FIG. 2d , like the other drawings, is aschematic drawing.

FIG. 2e schematically depicts an embodiment, wherein the anti-biofoulingsystem 200 comprises a plurality of UV emitting elements 210 (with aplurality of light sources), a plurality of radiation escape surfaces230, and a plurality of said parts 111, wherein the plurality of lightsources 220 are configured to provide said UV radiation 221 via saidplurality of radiation escape surfaces 230 to said plurality of parts111, and wherein said plurality of parts 111 are configured at differentheights of the object 10, and further comprising a plurality of saidwater switches 400, configured at the heights of the plurality of parts111, and wherein the anti-biofouling system 200 is configured to providesaid UV radiation 221 to said parts 111 when the respective waterswitches 400 are in physical contact with the water. Of course, theembodiment of FIG. 2e may optionally be combined with the embodimentschematically depicted in FIG. 2 c.

FIG. 2f schematically depicts an embodiment wherein a vessel 1, asembodiment of the object 10, comprises a plurality of anti-biofoulingsystems 200 and/or a one or more of such anti-biofouling systems 200comprising a plurality of UV emitting elements 210. Dependent upon theheight of the specific such anti-biofouling system 200 and/or the heightof the UV emitting elements 210, such as relative to a water (line), therespective UV emitting elements 210 may be switched on.

FIG. 3a schematically depicts an embodiment wherein the object, hereespecially the anti-biofouling system 200, further comprises a localenergy harvesting system 500 configured to harvest electrical energy andto provide said energy to said anti-biofouling system 200. Here, by wayof example a turbine is depicted which may provide electrical energywhen the vessel is moving in water. Hence, in embodiments the localenergy harvesting system 500 is comprised by said anti-biofouling system200. The local energy harvesting system 500 may e.g. comprise a solarcell, a turbine operating in water, a piezoelectric element operating ona pressure of waves, etc.

Especially, local energy harvesting systems may be applied that uponcontact with the water provide electrical energy, especially energyharvesting systems that provide electrical energy when submerged inwater and being subjected to a movement of water. FIG. 3b schematicallydepicts an embodiment wherein dependent upon the height of the specificanti-biofouling system 200 and/or the height of the UV emitting elements210, such as relative to a the water (line), the respective UV emittingelements 210 may receive electrical energy from the local energyharvesting system 500. Hence, especially the local energy harvestingsystem 500 may comprise one or more of a turbine operating in water anda piezoelectric element operating on a pressure of waves.

Alternatively or additionally, the local energy harvesting systemcomprises (i) a sacrificial electrode in electrical connection with afirst electrode of the light source 220, and (ii) a second energy systemelectrode in electrical connection with a second electrode of the lightsource 220, wherein the energy system is configured to provideelectrical power to said anti-biofouling system 200 when the sacrificialelectrode and the second energy system electrode are in electricalcontact with the water. Also such embodiment may be implemented in theconfiguration of FIG. 3b (see further for this embodiment FIGS. 5a-5c ).Of course, the embodiment of FIG. 3b may optionally be combined with theembodiments schematically depicted in one or more of FIGS. 2c and 2 e.

FIG. 4a shows a chicken-wire embodiment where light sources 210, such asUV LEDs, are arranged in a grid and connected in a series of parallelconnections. The LEDs can be mounted at the nodes either throughsoldering, glueing or any other known electrical connection techniquefor connecting the LEDs to the chicken wires. One or more LEDs can beplaced at each node. DC or AC driving can be implemented. If AC is used,then a couple of LEDs in anti parallel configuration may be used. Theperson skilled in the art knows that at each node more than one coupleof LEDs in anti parallel configuration can be used. The actual size ofthe chicken-wire grid and the distance between UV LEDs in the grid canbe adjusted by stretching the harmonica structure. The chicken-wire gridmay be embedded in an optical medium. Above, especially activeprevention applications are described, wherein the anti-biofoulingsystem 200 switches off, or switches specific UV emitting elements 210or specific light sources 220 off, dependent upon contact with thewater, a signal of a sensor, etc. etc. However, alternatively oradditionally, also warning signals or messages may be used to warn aperson of danger.

Hence, the invention also provides an object 10 that during use is atleast partly submerged in water, the object 10 further comprising ananti-biofouling system 200 comprising an UV emitting element 210,especially for application of UV radiation 221 to a part 111 of anexternal surface 11 of the object 10, wherein the UV emitting element210 comprises one or more light sources 220 and is configured toirradiate with said UV radiation 221 during an irradiation stage one ormore of (i) said part 111 of said external surface 11 and (ii) wateradjacent to said part 111 of said external surface 11, wherein the UVemitting element 210 comprises a UV radiation escape surface 230 andwherein the UV emitting element 210 is configured to provide said UVradiation 221 downstream from said UV radiation escape surface 230 ofsaid UV emitting element 210, with one or more of the functionalitiesindicated below.

For instance, in an embodiment the UV emitting element 210 comprises aluminescent material 260 configured to absorb part of the UV radiation221 and to convert into visible light 261, wherein the light source 220and said luminescent material 260 are configured to provide said visiblelight 261 (see FIGS. 4a-4b ) emanating in a direction away from theexternal surface 11 (see FIG. 4b ). Visible light in general isindicated with reference 291, and luminescent material light in thevisible is indicated with reference 261. For instance, alternatively oradditionally, the UV emitting element 210 comprises a second lightsource 280 configured to provide visible second light source light 281,such as especially red light, of which at least part emanates in adirection away from the external surface 11 (see this variant alsodepicted in FIG. 4a ). FIG. 4a schematically depicts a LED grid, thatmay e.g. be used in the UV emitting element 210 to provide UV radiation221 (and thus optionally also visible light 291.

In a specific embodiment, schematically depicted in FIGS. 4b and 4d (butoptionally implicitly also in FIG. 4c ) the anti-biofouling system 200may further be configured to provide visible light 291 emanating as alight beam 292 in a direction away from the external surface 11, whereinthe light beam 292 has a cross-section having the shape of a warningsign. FIG. 4c schematically depicts an arrangement of light sources 280,which may provide such warning signal (see FIG. 4d ). Note that FIG. 4cschematically depicts the light sources 280 configured to generatevisible light 291 (see FIG. 4d ). UV light sources 220 fill the rest ofthe area. The light source 280 are arranged in a warning signalconfiguration (and may e.g. lead to the beam shown in FIG. 4d ). Notethat instead of visible light emitting light sources 280 also UVemitting light sources 220 in combination with a luminescent materialmay be applied, or a combination of such variants.

In yet a further specific embodiment, the object 10 comprises e.g. avessel 1, wherein the UV radiation escape surface 230 is configured tothe external surface 11 of the object 10 at a position which ispermanent under the water (line) during use of the object 10. Forinstance, assuming a vessel, the UV emitting element(s) may beconfigured below the tropical fresh water load line (TF), or even belowthe freshwater load line (F), or below tropical zones load line (T), oryet even below the summer load line (S), or even below the winter loadline (W), yet even only below the winter North Atlantic load line (WNA).Hence, in embodiments the freeboard may be kept free from UV radiation(and from UV emitting element(s).

In yet another embodiment, schematically depicted in FIG. 4e the UVemitting element 210 is configured to provide at least 80% of the powerof the UV radiation in a direction within an angle θ of 0-90° from aperpendicular P to the earth's surface and in a direction below theobject 10, relative to the object during its use 10.

FIGS. 5a-5c schematically depicts some aspects of the anti-biofoulingsystem and its application. It is for instance an aspect of theinvention to insert UV LEDs and/or other light sources into anelectrical circuit that may already be available in an object 10 havinga (steel) external surface 11 and a sacrificial electrode 510 attachedthereto, see FIGS. 5a-5c for a comparison between the situation withoutUV emitting element 210 (FIG. 5a ), and with a light source (FIGS. 5band 5c ). The dashed line indicates by way of example an electricalreturn path through the steel external surface 11. The steel hull 21,here the external surface 11, may act as a second energy sourceelectrode 570. In this way, energy system 500 is provided, that may beused to power a light source or UV emitting element 210. FIG. 5b showsthe introduction of a UV emitting element 210 which may illuminate theexternal surface 11, and which may be powered by the energy system 500.

FIG. 5c schematically depicts in more detail an embodiment of theanti-biofouling system 200 (here also in an embodiment of the closedunit), wherein by way of example the UV emitting element 210 iscomprised by an optical medium 270. The anti-biofouling system isfurther elucidated amongst others with respect to this embodiment, butthe invention is not limited to this embodiment. FIG. 5c schematicallydepicts an anti-biofouling system 200 configured for preventing orreducing (water related) biofouling on a external surface 11 of anobject 10 that during use is at least temporarily exposed to anelectrically conductive aqueous liquid, by providing an UV radiation(anti-fouling light) 221 to said external surface 11.

Alternatively or additionally, the local energy harvesting system 500comprises (i) a sacrificial electrode 510 in electrical connection witha first electrode (not shown) of the light source or system 200 or UVemitting element 210, and (ii) a second energy system electrode 570 inelectrical connection with a second electrode (not shown) of the lightsource or system 200 or UV emitting element 210, wherein the energysystem 500 is configured to provide electrical power to saidanti-biofouling system 200 when the sacrificial electrode 510 and thesecond energy system electrode 570 are in electrical contact with thewater.

Hence, herein optical and/or electrical approaches are suggested toprovide extra safety when using UV radiation. One or more of theseapproaches may be applied simultaneously.

Optical approaches include amongst others:

The use of visible LEDs in series with a UV LED: UV light is harmful tohuman beings. What makes it more risky, is the fact that it isinvisible. This implies that human beings have no visible, audible orany other warning signs when they're exposed to UV light (This alsoexplains why sunburns are common). The safety idea proposed here is tohave a visible LED (e.g. bright red) in series with a UV LED. Because ofthe series connection, the visible LED will “always” be on when the UVLED is on, thus giving a clearly visible warning sign.

The combination of a visible+UV light in direct series connection can bea very fundamental safety building block.

Alternatively or additionally, a number of visible LEDs can be organizedin a pattern on the hull of a ship, to e.g. show a warning symbol, likea triangle or exclamation mark.

Another approach is to embed a phosphor in the coating, near the UVsource. This phosphor should convert the UV light to a visible lightwavelength. Again, the phosphor can be arranged in a pattern thatconveys a warning; like above.

Electrical approached include amongst others:

LEDs switched on only when in contact with water. Different embodimentscan be envisioned:

A (temporary) contact with water flips a switch, and the whole system(or subsection) of LEDs stay on (for a pre-determined period of time)

At LED level: a second electrode of the LED is directly connected to thewater, implying that a closed circuit is only obtained when the LED issubmerged; the water is the return electrode.

Alternatively, the water can close a small gap in the circuit for eachindividual LED (or section of LEDs).

Further, mechanical and system approaches are proposed herein. One ormore of these approaches may be applied simultaneously. With ‘systemapproaches’, it is especially meant that the safety of the entireapplication (such as an entire vessel) is controlled at a system level.That is, the entire system (or large parts or subsections) arecontrolled at once.

System approaches include amongst others:

As the UV light is mainly emitted on the lower side (and outside) of thehull, people on board the ship hardly have a line of sight to the UVemitting layers. Hence they are not at risk of UV exposure. This isdifferent for people outside of the boat; most relevant when a boat isdocked in harbor. In that scenario, people are walking on the docks, andsmall supply vessels are sailing around the boat (fuel supply shipsetc.).

An embodiment is to use a sensor that detects movement and/or presence(via infrared light, generated by human beings and or small engines ofsmall boats or cars). When movement or presence is detected, the entireUV system (or parts of it) will be switched off (temporarily). The ideais similar, yet opposite, to common household systems, where a light onthe outside of a house (i.e. on the porch) is turned ON when presence ormotion is detected. We switch our (UV) lights OFF.

Optionally, also a timer may be employed to switch on the light againafter a predetermined period of time without movement being detected.

Design approaches include amongst others:

As the absorption of water for UV light is fairly high, only LEDs abovethe waterline (or within the first 0.50 m) may emit light that actuallyreaches human beings (assuming they're above the water line and notswimming around the boat). Hence, only LEDs may be configured on‘deeper’ sections of the boat, and/or only turn on the upper sections(close to the waterline) in ‘inherently safe’ circumstances, like whensailing on the open ocean. This may require the LEDs to be arranged inhorizontal, striped sections, of e.g. 1 meter in height, which can becontrolled individually. The actually loading of the ship may then beused to decide which sections to turn on.

In a further embodiment the LEDs are only applied on the lowest parts ofthe boat; that never get above the waterline, not even on an emptyvessel.

The layout of the LEDs in the optical structure may be designed suchthat the light is emitted primarily outwards (as needed for allapplications) and downwards. This may not completely eliminate any UVlight of “escaping to above the waterline”, but it will severely limitthe amount.

Hence, safety improvements for an UV based anti-fouling system areproposed. The various embodiments can be used individually and/or incombinations of one or more. Thus, the risk of UV light reaching humaneyes may substantially be reduced (to an acceptable level).

The term “substantially” herein, such as in “substantially all light” orin “substantially consists”, will be understood by the person skilled inthe art. The term “substantially” may also include embodiments with“entirely”, “completely”, “all”, etc. Hence, in embodiments theadjective substantially may also be removed. Where applicable, the term“substantially” may also relate to 90% or higher, such as 95% or higher,especially 99% or higher, even more especially 99.5% or higher,including 100%. The term “comprise” includes also embodiments whereinthe term “comprises” means “consists of”. The term “and/or” especiallyrelates to one or more of the items mentioned before and after “and/or”.For instance, a phrase “item 1 and/or item 2” and similar phrases mayrelate to one or more of item 1 and item 2. The term “comprising” may inan embodiment refer to “consisting of” but may in another embodimentalso refer to “containing at least the defined species and optionallyone or more other species”.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequential orchronological order. It is to be understood that the terms so used areinterchangeable under appropriate circumstances and that the embodimentsof the invention described herein are capable of operation in othersequences than described or illustrated herein.

The devices herein are amongst others described during operation. Aswill be clear to the person skilled in the art, the invention is notlimited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.Use of the verb “to comprise” and its conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Thearticle “a” or “an” preceding an element does not exclude the presenceof a plurality of such elements. The invention may be implemented bymeans of hardware comprising several distinct elements, and by means ofa suitably programmed computer. In the device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

The invention further applies to a device comprising one or more of thecharacterizing features described in the description and/or shown in theattached drawings. The invention further pertains to a method or processcomprising one or more of the characterizing features described in thedescription and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order toprovide additional advantages. Furthermore, some of the features canform the basis for one or more divisional applications.

The invention claimed is:
 1. A vessel that during use is at least partlysubmerged in water, the vessel comprising: an ultraviolet (UV) lightemitting element in or on an external surface of the vessel, wherein theUV light emitting element includes one or more light sources and isconfigured to emit UV radiation in a direction away from the externalsurface of the vessel to irradiate with the UV radiation a portion ofthe water adjacent to a part of the external surface of the vessel; anda water switch, wherein the water switch is connected in an electricalcircuit in series with a power source and the UV light emitting element,and wherein the water switch is configured to be closed by the wateracting as a conductor in the electrical circuit between the power sourceand the UV light emitting element so as to complete the electricalcircuit and provide power from the power source through the water to theUV light emitting element, and to cause the UV light emitting element toproduce the UV radiation, and wherein when the water is not present atthe water switch the water switch is open and the UV light emittingelement does not emit the UV radiation.
 2. The vessel of claim 1,further comprising a local energy harvesting system, wherein the localenergy harvesting system is configured to harvest electrical energy andto provide said harvested electrical energy to said UV light emittingelement.
 3. The vessel of claim 2, wherein the local energy harvestingsystem is selected from the group consisting of a solar cell, a turbineoperating in water, and a piezoelectric element operating on a pressureof waves.
 4. The vessel of claim 1, wherein the UV light emittingelement includes a UV radiation escape surface, and wherein the UVradiation escape surface is configured as part of said external surfaceof the vessel.
 5. The vessel of claim 1, wherein the UV light emittingelement comprises a luminescent material, wherein the luminescentmaterial is configured to absorb part of the UV radiation and convertthe absorbed part of the UV radiation into visible luminescent light,wherein the UV light emitting element is configured to provide saidvisible luminescent light emanating in a direction away from theexternal surface.
 6. The vessel of claim 1, further comprising a visiblelight emitting device, wherein the visible light emitting device isconnected in series with the UV light emitting element, and isconfigured to provide visible light emanating as a visible light beam inthe direction away from the external surface in response to the UV lightemitting element being turned on and emitting the UV radiation, whereinthe visible light beam has a cross-section having a shape of a warningsign.
 7. The vessel of claim 1, wherein the external surface comprises aUV radiation escape surface through which the UV light passes from theUV light emitting element, and wherein the UV radiation escape surfaceis provided at a position which is permanently under a water line of thewater during use of the vessel.
 8. The vessel of claim 1, wherein the UVlight emitting element is configured to provide at least 80% of thepower of the UV radiation in a direction within an angle of 0-90° from aperpendicular to the earth's surface and in a direction below thevessel, relative to the vessel during its use.
 9. The vessel of claim 1,wherein the water switch is disposed at a height which is higher withrespect to a water line of the water than the UV light emitting element.10. A vessel that during use is at least partly submerged in sea water,the vessel comprising: an ultraviolet (UV) light emitting elementattached to a hull of the vessel, wherein the UV light emitting elementincludes one or more light sources and is configured to irradiate withUV radiation a portion of the sea water adjacent to a part of the hullof the vessel; and a water switch, wherein the water switch is connectedin an electrical circuit in series with a power source and the UV lightemitting element, and wherein the water switch is configured to beclosed by the sea water, wherein the sea water itself is a conductor inthe electrical circuit between the power source and the UV lightemitting element so as to complete the electrical circuit and providepower from the power source through the sea water to the UV lightemitting element, and cause the UV light emitting element to produce theUV radiation, and wherein when the sea water is not present at the waterswitch the water switch is open and the UV light emitting element doesnot emit the UV radiation.
 11. The vessel of claim 10, furthercomprising a local energy harvesting system is configured to harvestelectrical energy and to provide the harvested electrical energy to theUV light emitting element.
 12. The vessel of claim 10, wherein the UVlight emitting element comprises a luminescent material, wherein theluminescent material is configured to absorb part of the UV radiationand convert the absorbed part of the UV radiation into visibleluminescent light, and wherein the UV light emitting element isconfigured to provide the visible luminescent light emanating in adirection away from the hull of the vessel.
 13. The vessel of claim 10,further comprising a visible light emitting device connected in serieswith the UV light emitting element, wherein the visible light emittingdevice is configured to provide visible light emanating as a visiblelight beam in a direction away from the hull of the vessel in responseto the UV light emitting element being turned on and emitting the UVradiation, wherein the visible light beam has a cross-section having ashape of a warning sign.